The purpose of this research study is to determine the safety of RAD001 and the highest dose of this drug that can be given to people with HER2-positive metastatic breast cancer safely in combination with trastuzumab. RAD001 has been used in patients with severe rheumatoid arthritis, in recipients of solid-organ transplants, healthy volunteers and experiments with animals, and information from those other research studies suggest that this RAD001 may help to stop cancer cells from growing abnormally.